//
// Created by wze-zero on 2024/7/15 015.
//
#include <iostream>

using namespace std;

int getSum(int n);

int main() {
    int n;
    cin >> n;
    cout << getSum(n) << endl;
    return 0;
}

int getSum(int n) {
    if (n == 1 || n == 2) {
        return 1;
    } else {
        return getSum(n - 1) + getSum(n - 2);
    }
}